1. Field of the Invention
This invention relates to the processing of tobacco leaf material in the manufacture of smoking articles.
2. Brief Description of Related Art
Tobacco leaves of the types used in the manufacture of cigarettes and like smoking articles comprise leaf lamina, a longitudinal main stem (rib) and veins extending from the main stem. The main stem and large veins are hereinafter jointly referred to as `stem`. The stem has substantially different physical properties from the lamina, and it is long-established practice to separate the stem from the lamina at an early stage in the processing of tobacco leaves, the stem and lamina then being processed independently and differently.
The manner in which stem material is separated from lamina material is generally by means of a complex and large threshing plant comprising a number, eight for example, of serially arranged threshing machines with classification units disposed intermediate next adjacent threshing machines.
As is well known, the separated stem material, or a proportion of it, after suitable reduction in size, is often added back to the lamina after the lamina has been subjected to further processing. Stem material is often desirable in the tobacco blend to improve fill value.
It is an object of the invention to provide an improved method of processing tobacco leaf material to provide a product suitable for use in smoking articles, cigarettes and cigars for example.
We have looked at ways of simplifying the overall tobacco producing process from leaf to smoking article.
We have found that it is possible to use a mill for the purpose of operating simultaneously on stem and lamina to produce a product useful for incorporation in smoking articles. Whilst we are aware that it has been proposed to use a disc mill to reduce the particle size of stem material on its own, we are not aware of any use of a single mill wherein whole leaf is fed to the mill so as to make possible the provision of a particulate material which is capable of being used for making smoking articles without any substantial further size-reduction process. It has, however, been found to be possible to use a mill with whole leaf, as defined hereinafter, to produce a mixture of particulate lamina material, and substantially intact stem material, the lamina material having a size which makes it suitable for being used, without further substantial size reduction, in the making of smoking articles. Thus, for instance, the lamina material can be fed to a commercial cigarette rod making machine, a Molins Mk 9 for example.
By `whole leaf` we mean complete, or substantially complete, leaves or leaves which have been reduced in size by a reduction process, such as chopping or slicing for example, that does not involve any significant separation of lamina and stem. The leaves or leaf portions will generally have been cured and may have been subject to other more or less conventional treatments.
Prior proposals for the processing of tobacco leaves to provide filler for cigarettes and like smoking articles are numerous. Examples are to be found in the following patent specifications:
Germany (Federal Republic): 954,136 PA1 New Zealand: 139,007 PA1 United Kingdom: 1855/2134; 413,486; 2,026,298; 2,078,085; 2,118,817; 2,119,220 and 2,131,671 PA1 United States: U.S. Pat. Nos. 55,173; 68,597; 207,140; 210,191; 250,731; 358,549; 360,797; 535,134; 2,184,567; 3,026,878; 3,128,775; 3,204,641; 3,690,328; 3,845,774; 4,195,646; 4,210,157; 4,248,253; 4,323,083; 4,392,501; 4,582,070; 4,696,312 and 4,706,691.